1. Field of the Invention
The present invention relates to an insulated tie plate for bracing and securing a railroad rail.
2. Description of Related Art
A rail system is generally divided into sections or blocks for detecting trains which permit more trains to travel on one stretch of track or railroad rails. Each section is electrically isolated from all other sections so that when no train is present, a high electrical resistance can be measured over the parallel railroad rails in that section. When a train enters the section, the train short circuits adjacent railroad rails and the electrical resistance drops, thus indicating that a train is in that section.
A tie plate, typically made of metal, is used to secure a railroad rail against lateral, rotational, and vertical movements. Railroad rails are generally joined to each other by welding each end or by attaching the ends using a steel rail joint. Electrically isolating the joined rails from each other is necessary for signaling and other control functions. When two railroad rail sections are joined using a typical metal tie plate, electrical isolation of the railroad rail sections may not occur because the current will pass from one railroad rail section through the tie plate and then to the adjacent railroad rail section. Non-metallic insulating tie plates are sometimes utilized, but are generally expensive because of the special high-performance materials needed to endure the high tensile and flexural forces acting on the railroad rail. Thus, metallic tie plates having a coating of electrically-insulating material is utilized. The electrically-insulating material, however, will wear after a period of use and may cause undesired shorting between the rails and the tie plate. The electrically-insulating material will need to be replaced or the metallic tie plate having the electrically-insulating coating will need to be replaced.
Referring to FIG. 1, a conventional tie plate assembly 1 includes a tie plate 2 that defines a recessed portion 4 for receiving a base portion 6 of a rail 8. The recessed portion 4 of the tie plate 2 receives electrically-insulating material in the form of a bottom plate 10 and two side plates 12. The tie plate 2 is secured to a tie (not shown) via fasteners 14. The rail 8 is secured to the tie plate 2 via clips 16 that are secured to the tie plate 2 with fasteners 18. In particular, the clips 16 engage rail joint bars 20 that secure adjacent rail sections to each other. The tie plate assembly 1 is shown in FIG. 15 of U.S. Pat. No. 8,042,747, which is hereby incorporated by reference in its entirety.